A technique that will adequately describe the physical condition of water in the soil has long been desired by scientists. The method should include the effect of soluble materials on the osmotic pressure of the soil solution, and also the effect of surface force action between the soil and soil water. Parker (8) demonstrated that the freezing point was reduced in the presence of finely divided material. This suggested the possibility of using the cryoscopic procedure to measure the physical condition of water soil. More recently, the introduction of Thermistors for accurate temperature measurement have made it desirable to investigate in greater detail the freezing point of water in soil. The experimental work reported here deals with the freezing point of water in soil and its relation to soil moisture tension as determined on three soils in a puddled and unpuddled condition. Several freezing treatments were included in this study to investigate improvements in the freezing technique. The treatments were arranged in a standard split plot experimental design. Eighteen hundred freezing measurements were made and analyzed statistically.

Le patrimoine ferroviaire français comporte de nombreux ponts métalliques, principalement construits au cours de la seconde moitié du XIXème siècle. Ces ouvrages d'art sont donc en service depuis plus d’un siècle et nécessitent une politique de maintenance adaptée. En collaboration avec SNCF Réseau, cette thèse de doctorat apporte des éléments de compréhension sur le comportement mécanique des assemblages rivetés à chaud sous sollicitations monotones et cycliques. Une stratégie expérimentale a été mise en oeuvre afin d'identifier les mécanismes de ruine des assemblages rivetés. Dans un premier temps, le matériau objet de cette étude, un fer puddlé, a été extrait d'éléments provenant du pont sur l'Adour à Bayonne (1864-2013). Ce matériau a été notamment caractérisé sous chargements monotones et cycliques ; sa fragilité, son anisotropie et son comportement dispersif ont été mis en évidence et analysés. Des outils numériques ont été développés pour l’étude microscopique de cette famille de matériaux. Des éprouvettes rivetées de type détail constructif ont par la suite été conçues, fabriquées et testées sous chargements monotones et cycliques. Un scénario précis du fonctionnement et de ruine d'un assemblage mono-rivet en double recouvrement a pu être identifié. Pour cela, les influences des caractéristiques matériau, des concentrations de contraintes, du cisaillement du rivet et de l'effort de serrage ont été étudiées. Les résultats de ce travail, comparés à ceux de la littérature et aux standards de dimensionnement des structures métalliques, montrent la complémentarité d'une étude à plusieurs échelles (comportement matériau et étude locale du fonctionnement des assemblages) dans le but de comprendre et estimer le comportement des structures rivetées anciennes. / Numerous metallic bridges can be found in the French railway heritage. Since a majority of these structures was built during the second half of the 19th century, they have been in service for over a hundred years and need an adapted maintenance policy.These doctoral thesis, done in collaboration with SNCF Réseau, improves the understanding of the mechanical behaviour of hot riveted assemblies under monotonic and cyclic loadings. An experimental strategy was proposed and carried out in order to identify the failure mechanisms of riveted assemblies. First, the studied material, a puddled iron, was obtained from recovered elements from the bridge over the Adour river in Bayonne (1864-2013). Mechanical testing and characterisation was performed under monotonic and cyclic loadings. Puddled iron’s brittle, anisotropic and scattered behaviour was observed and analysed. In-house software applications were developed in order to study this kind of material. Additionally, hot riveted specimens (constructional details) were designed, manufactured and tested under monotonic and cyclic loadings. A precise working (and failure) scenario of the double shear mono-rivet assembly was identified. The influence of the material’s behaviour, stress concentrators, shearing of the rivet and clamping force of the rivet were studied. The results obtained during these research works, compared to the ones found in academic literature as well as construction norms for metallic structures, showed the importance and complementarity of a multi-scale approach (material behaviour and local study of assemblies) in order to understand and assess the behaviour of ancient riveted structures.